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Measuring & Mapping

Where, how far, and how much? People have invented an astonishing array of devices to answer seemingly simple questions like these. Measuring and mapping objects in the Museum's collections include the instruments of the famous—Thomas Jefferson's thermometer and a pocket compass used by Meriwether Lewis and William Clark on their expedition across the American West. A timing device was part of the pioneering motion studies of Eadweard Muybridge in the late 1800s. Time measurement is represented in clocks from simple sundials to precise chronometers for mapping, surveying, and finding longitude. Everyday objects tell part of the story, too, from tape measures and electrical meters to more than 300 scales to measure food and drink. Maps of many kinds fill out the collections, from railroad surveys to star charts.

This sextant has a brass frame. The silvered scale is graduated every 10 minutes from -5° to +145° and read by vernier with tangent screw and swinging magnifier to single minutes of arc. The inscriptions read "Frodsham, Liverpool" and "2602." It came from Vassar College, and may have been used by the professor of astronomy, Maria Mitchell.

Matthew Berge (d. 1819) worked for Jesse Ramsden in London, succeeded to the business after Ramsden’s death in 1800, used the Ramsden dividing engine, and numbered his sextants in the sequence begun by Ramsden. This example was made in the early 1800s. It has a "double" brass frame and a silvered scale. The signature on the arc reads "Berge London late Ramsden." The scale is graduated every 15 minutes from -2° to +136° and read by vernier with tangent screw and magnifier.

A label in the box relates the instrument’s history. "SEXTANT owned and used by JOHN C. FREMONT on his trip across the continent to CALIFORNIA. Presented by his Daughter, ELIZABETH B. FREMONT, to HON. CHARLES SILENT and by him to FRANK J. THOMAS. Loaned to and used by WELLS MORRIS on U.S. Destroyer "MUGFORD" in GREAT WAR." The sextant bears the engraving, "Berge London late Ramsden" and "1513".

Ref: A. Stimson, "The Influence of the Royal Observatory at Greenwich upon the Design of 17th and 18th Century Angle-Measuring Instruments at Sea," Vistas in Astronomy 20 (1976): 123-130.

The double-framed brass sextant was patented by Edward Troughton in London in 1788, and the form remained popular throughout the first half of the 19th century. This example belonged to Haverford College in Pennsylvania and may have been acquired when that school was founded in 1833. It has a silvered scale that is graduated every 10 minutes from -5° to +145° and read by vernier with tangent screw and swinging magnifier. The inscription reads "W. & S. Jones Holborn London."

Ref: Edward Troughton, "Framing to be used in the construction of octants, sextants, and quadrants," British patent #1644.

This sextant belonged to Haverford College, and probably dates from the second half of the 19th century. The frame is brass. The silvered scale is graduated every 15 minutes from -5° to +130° and read by vernier with tangent screw and swinging magnifier to single minutes of arc. The arc is engraved "JOHN BRUCE & SON, Liverpool."

This sextant is somewhat unusual in that it has a brass frame, reinforced brass index arm, and ivory (rather than metal) scale. This scale is graduated every 10 minutes from -5° to +125° and read by vernier with tangent screw and swinging magnifier to 20 minutes of arc. The "Spencer Browning & Co., London" inscription on the arc refers to a firm that was in business from 1840 to 1870.

This sextant has a brass frame. The silvered scale is graduated every 10 minutes from -5° to +145° and read by vernier with tangent screw and swinging magnifier to 10 seconds of arc. The "Spencer Browning & Rust LONDON" inscription on the arc refers to a firm that was in business from 1784 to 1840.

This instrument is a specialized timekeeper for finding longitude at sea. Thomas Earnshaw made this chronometer in England about 1798. It became part of the James Arthur Collection at New York University, and the university donated a portion of the collection, including this chronometer, to the Smithsonian in 1984.

To find longitude at sea, a chronometer was set to the time of a place of known longitude, like Greenwich, England. That time, carried to a remote location, could be compared to local time. Because one hour of difference in time equals 15 degrees difference in longitude, the difference in time between the chronometer and local time would yield local longitude. The instruments require careful handling to keep precise time. Although the original box for this instrument has not survived, most chronometers are fitted in a wooden box in a gimbal to remain level and compensate for the movement of a ship at sea.

Thomas Earnshaw (1749-1829) was a pioneer in chronometer development. He is credited with introducing to chronometer design two important features that became standard parts of the timekeeper in the 19th century—the detached detent escapement and, independently of his rival John Arnold, the bimetallic compensation balance. His simplifications permitted others to undertake batch production of chronometers, and his work received an award of £2500 from Britain’s Longitude Board in 1805.

This instrument, made by John Roger Arnold about 1825, is a specialized timekeeper for finding longitude at sea. The chronometer was part of the James Arthur Collection at New York University, and the university donated a portion of the collection, including the chronometer, to the Smithsonian in 1984.

To find longitude at sea, a chronometer was set to the time of a place of known longitude, like Greenwich, England. That time, carried to a remote location, could be compared to local time. Because one hour of difference in time equals 15 degrees difference in longitude, the difference in time between the chronometer and local time would yield local longitude. The instruments require careful handling to keep precise time. Although the original box for this instrument has not survived, most chronometers are fitted in a wooden box in a gimbal to remain level and compensate for the movement of a ship at sea.

John Roger Arnold (1769-1843) learned watchmaking from his father, chronometer pioneer John Arnold, and Abraham Louis Breguet. The Arnolds were in business as Arnold & Son between 1787 and 1799, when the father died. In 1805 John Roger Arnold accepted the English Board of Longitude’s posthumous award to his father for improvements to the marine chronometer, which included simplifications that permitted others to undertake batch production of chronometers—a detached escapement, a helical balance spring and a temperature-compensated balance. The younger Arnold continued the business and between 1830 and 1840 took in partner Edward John Dent. In that decade, the firm made about 600 chronometers.

Edward Troughton, of London, introduced this type of reflecting circle in 1796. The telescope, mirror, and filters are on one side of the circle, while the silver scale is on the other. This scale is graduated to 20 minutes, and read by three verniers (one has a tangent screw) to 20 seconds. The circle is supported on a heavy brass stand with a counterweight. The inscription reads "Troughton & Simms 240 LONDON." Troughton & Simms were still offering instruments of this sort in the 1850s–at a cost of £23. This example belonged to Worcester Polytechnic Institute, and was probably made in the late 1830s.

This watch belonged to Sir Sandford Fleming, chief engineer of the Canadian Pacific Railway. About 1880, Fleming devised a plan for worldwide time zones and had a complicated watch made to reflect both zoned time and local time.

The maker of Fleming's watch is the London firm of Nicole, Nielsen & Co. Successor to a business founded by Swiss immigrants Adolphe Nicole and Jules Capt in the late 1830s, the firm made high-quality timepieces. Fleming ordered the watch through retailer E. White, also of London.

Fleming's first notions about time reform emerged on a trip to Ireland in 1876, when he missed a train because he misread a timetable. His initial plan concentrated on replacing the two twelve-hour designations of the day, A.M. and P.M., with a twenty-four hour system. Almost immediately, though, he expanded his ideas about time reform to propose a system he called variously "Terrestrial Time," "Cosmopolitan Time," and "Cosmic Time"-a division of the globe into twenty-four zones, each one hour apart and identified by letters of the alphabet.

As the 1880s began there was no binding international agreement about how to keep time for the world. Traditionally, each country used its own capital city or main observatory for measuring time and designating lines of longitude on national maps. After publication of the British Nautical Almanac began in 1767, many nations came to use Greenwich time for navigation and some scientific observations. Local mean time served for all other activities.

Added emphasis on Greenwich had come from North America when the railroads there voluntarily adopted a standard zoned time in 1883. In that system, the zones were based on meridians counted west from Greenwich, England, at zero degree of longitude.

Fleming was not the first or only proponent of world standard time. Quirico Filopanti, an Italian mathematics and engineering professor, for example, published a scheme based on twenty-four zones counted from Rome as prime meridian in 1858.

Organized international support emerged slowly for fixing a common prime meridian. Not until October 1884 did diplomats and technical specialists gather to act on scientific proposals. The International Meridian Conference, held in Washington, DC, recommended that the nations of the world establish a prime meridian at Greenwich, count longitude east and west from the prime meridian up to 180 degrees in each direction, and adopt a universal day beginning at Greenwich at midnight. Although the International Meridian Conference had no authority to enforce its suggestions, the meeting resulted in the gradual worldwide adoption of a time-zone based system with Greenwich as zero degrees.

The military and some civilian science, aviation and navigation efforts still use alphabet identifiers for time zones. The time of day in Zone Z is known as "Zulu Time." The zone is governed by the zero degree of longitude that runs through Greenwich.